1. Field of the Invention
The present invention relates to medical devices comprising self-blunting needles and to methods of manufacture of such self-blunting needle medical devices. More specifically, this invention is directed to improved medical devices of the type including a needle and blunting member which are movable relative to each other and to a method of manufacture thereof.
2. Related Art
For reasons which have received wide publicity, there is substantial demand for single-use venipuncture products which may be employed by health care workers with minimal risk of incurring an accidental needle-stick wound. A highly successful product of this nature is a self-blunting needle assembly sold under the registered trademark "PUNCTUR-GUARD" by Bio-Plexus, Inc. of Vernon, Connecticut. The "PUNCTUR-GUARD" needle assembly is manufactured in accordance with the teachings of U.S. Pat. No. 4,828,547, entitled "Self-Blunting Needle Assembly and Device Including the Same", issued on May 9, 1989 to Carl R. Sahi et al. This patent is hereby incorporated by reference herein. In the "PUNCTUR-GUARD" product, a rod or probe-like blunting member is disposed within the bore of a needle cannula having a (usually beveled) puncture tip suitable for puncturing tissue. To prevent accidental needle-stick wounds from occurring after use of the device, the blunting member, which is retracted behind the puncture tip when the needle is injected into tissue, can be extended beyond the puncture tip of the needle cannula to effectively blunt the puncture tip by extending beyond it, so as to eliminate or at least greatly reduce the risk of accidental needle-stick punctures.
During production of self-blunting venipuncture products such as the "PUNCTUR-GUARD" needle assembly discussed above, the blunting member must be inserted into the back of the needle cannula. This is a process step which requires high placement accuracy. This high placement accuracy has, in the past, been achieved through the use of an adjustable position blunting member inserter which is responsive to signals provided by an optical sensor system. This process requires that the needle cannula be mounted in a hub to form a front needle sub-assembly and then positioned over a light source. If alignment conditions were perfect, light from the source would enter the beveled tip of the front needle, pass through the length of the front needle, and exit the back of the front needle as a perfect, i.e., circular, beam of light. The optical system would detect the circular beam of light, compute its position and generate control signals which would direct the blunting member inserter to bring the blunting member cannula into alignment with the front needle cannula.
Since alignment conditions are never perfect, it is difficult to detect the circular beam of light which is commensurate with precise alignment, i.e., variations within the components allow the front needle cannula to be slightly tilted within the front needle sub-assembly. The projected light beam may thus be located in an infinite number of locations. The optical system must, accordingly, locate the unique light beam for each individual front needle cannula and hub and then direct the blunting member sub-assembly inserter to this unique position for proper placement. Further, while the combination of the optical system and inserter can locate the back of the front needle cannula very accurately and then move the inserter to a position commensurate with the location, it does not precisely locate the blunting member which, of course, must enter the back of the front needle cannula for successful insertion. Thus, slight variations in the blunting member sub-assembly itself or misalignment in the clamping of the blunting member sub-assembly by the inserter can cause a failure to accurately mate the blunting member sub-assembly with the front needle sub-assembly. In summary, the step of insertion of the blunting member cannula into the back of the front needle cannula is inefficient and time-consuming.
When the above-described self-blunting needle technology is employed in a fluid collection needle, the fluid to be collected is drawn through the blunting member cannula and into an evacuated tube. Leakage of air through the space inherently existing between the blunting member outer diameter and the front needle inner diameter, such air thereafter flowing through the blunting member cannula into the collection tube, will cause undesirable foaming in the collection tube. Accordingly, in order to be suitable for use in a blood collection system, a self-blunting needle assembly must pass an air seal test. The requisite seal between the blunting member and front needle must be achieved in a manner which does not significantly impede the above briefly discussed assembly process or impede relative movement between the blunting member cannula and the needle cannula.
Therefore, there remains a need in the art for methods and apparatus which facilitate the manufacture of medical devices employing self-blunting needle technology.
Additionally, there remains a need in the art for methods and apparatus for preserving the integrity of fluid transferred through medical devices employing self-blunting needle technology by providing an improved fluid flow seal between the various components of such medical devices.